The battery in my late-2008 model aluminium 13" MacBook became extremely swollen in early to mid-2012 after only 283 cycles (as per
Cycle count under
Power), and the button on the multi-touch trackpad stopped working due to the expansion of the battery. I have since had to remove the battery to get the button working again, but the battery itself hasn't leaked, just expanded very heavily to nearly 1.5× the height (perhaps ≈0.2 each on top and bottom). After removing it, it's basically nearly impossible to put it back in and still close the cover.
I'm convinced that this is a fault in Apple's design, because it seemingly started after there were a couple of times that I had a browser open with too many windows, and it busy-looped during the night, getting quite hot and with the fan kicking in. However, during such occasions, the MacBook itself sat on a rather clear desk in an air-conditioned room, so I find it unacceptable that plain-use self-overheating on the machine's part could possibly cause any such problems. (I only ever ran OS X on the machine, and it was very far away from any other heat sources or direct sunlight.)
I'm disappointed that now I not only can't use the MacBook as a portable with any kind of battery life at all, but also that it is now subject to resets during power outages and cannot be transported (e.g. in sleep mode) without having to be shutdown first.
Shouldn't extremely swollen and expanded batteries that completely obstruct trackpad button usage be covered by a warranty? This never happens with any other single brand-name manufacturer of computer batteries! What are my options? Do I have to buy another battery at full price, only to have it become pregnant and start obstructing my button again right after the warranty is out? I tried going to an Apple Store in NorCal, and they said they can't do anything about it, since it's out of warranty. They said that even at 1.5× the width, it is still supposedly safe to use!
My perspective here is that the battery has not been consumed, but instead became damaged through no fault of my own. It was either defective outright (either through design or manufacturing), or it has become damaged through hardware/firmware/software bugs related to charging and/or overheating. I wouldn't have cared if it simply stopped holding the charge for more than a dozen of minutes or so; that's clearly something that is very well documented everywhere and is to be expected.